ADA4177-2ARMZ-R7 datasheet(24/31 Pages) AD

Part #	ADA4177-2ARMZ-R7

Description	OVP and EMI Protected, Precision, Low Noise and Bias Current Op Amps

PDF	31 Pages

Scroll/Zoom	100%

Manufacturer	AD [Analog Devices]

Direct Link	http://www.analog.com

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24 / 31 page

ADA4177-1/ADA4177-2/ADA4177-4

Data Sheet

THEORY OF OPERATION

The ADA4177-1, ADA4177-2, and ADA4177-4 are precision,

bipolar op amps that integrate both input overvoltage protection

(OVP) and input EMI filtering while maintaining a low 2 nA

maximum bias current and a rail-to-rail output operation.

Figure 84 shows a conceptual schematic of the main amplifier

that uses super beta, bipolar input transistors and bias current

cancellation to minimize the input bias current. The inputs are

cascoded to protect the super beta input devices from damage

during overvoltage conditions. The cascoded inputs feed into an

active load that makes up the primary gain stage. A buffered

transconductance (gm) stage converts a differential voltage to a

differential current to drive the output stage. The rail-to-rail

output can swing to 50 mV maximum (for example, the

guaranteed room temperature limit for VOH is 14.95 V when

the positive supply is 15 V) with a 1 mA load at 25°C.

Figure 84. Conceptual Schematic

Rev. C | Page 24 of 31

ADA4177-2ARMZ-R7 Datasheet(PDF) 24 Page - Analog Devices